A control system basically includes a control device (a switch for example) connected, by means of circuitry, to apparatus it controls.
In simple systems each control device is connected directly to the apparatus it controls, thus necessitating a generally independent system for each piece of appartus to be controlled.
In a more advanced electronic system replacing several independent systems, the control devices are connected to their respective pieces of apparatus to be controlled via a processing computer. Thus information from each control device is available to the system as a whole. Furthermore, in this case the various control devices may share common circuitry. This physically reduces the amount of wiring but requires that each control device must have its own characteristic signal code. As a corollary, there must be a de-coding arrangement to provide correct routing of control signals.
These electronic control systems have grave disadvantages in that they tend to cause radio frequency emissions, which may, in a war-like environment, be of sufficient magnitude to attract the attention of an enemy, who can then apply electronic counter measures or launch weapons against the vehicle. In the latter case, the emissions may be of sufficient magnitude to provide homing for a weapon guidance system. A further disadvantage is that, even in a non war-like environment, high energy transmissions from radar or radio stations can cause interference with the correct functioning of such a control system.
One object of the present invention is to provide a control system which not only does not emit to radio frequencies but also is not susceptible to outside interference.
A further objective is to provide a control system which is readily adaptable to change so that changes can be cheaply and rapidly made to suit new requirements.
It is yet a further objective to provide a control system which is robust, simple, has few moving parts, and is sufficiently lightweight to be used in aircraft embodiments.
The invention utilizes one or more control devices such as a push-button, rotary or toggle switches and circuitry associated therewith in which, the circuitry comprising light guide means with light emitting means and light receiving means, the control device having a movable element with modulation means associated with the movable element arranged to vary the light transmitted between the light emitting means and the light receiving means in response to movement of the movable element. Such control devices have been described generally in IBM technical disclosure bulletin Vol. 20, No. 2, July 1977.
Preferably where there is a plurality of control devices, the modulation means of each is provided with coding means to provide each with its own signalling code. In this case, the light guide means may comprise a single input light guide, including light splitting means for directing a proportion of the light therein to the light emitting means of a control member for coding, whilst transmitting the remainder to a further splitting means, and a single output light guide means including light combining means for combining the modulated output into the single output light guide. An arrangement such as this is described generally in IBM technical disclosure bulletin Vol. 17, No. 3, August 1974.
The light guide means may comprise, instead of separate input and output light guides, a single light guide combining the functions of both. In this case, the function of light emitting and receiving can be combined in a series of individual emitting/receiving means. Similarly, the light splitting and combining functions can be combined in a series of individual splitting/combining means.